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LLY vs LBZ: What Every Truck Enthusiast Should Know

Last Updated on Aug 16, 2023 By Lillian Kazmierczak

The LLY refers to the 6.6-liter Duramax V8 engine that was produced from 2004 to 2005 and used in GM’s heavy-duty trucks such as the Chevrolet Silverado and GMC Sierra.

On the other hand, the LBZ is the updated version of the 6.6-liter Duramax V8 engine manufactured from 2006 to 2007. With several improvements over the LLY, including a stronger block, updated fuel system, and improved injectors, the LBZ was also suited to GM’s heavy-duty trucks.

The LBZ engine is more reliable and durable than the LLY with the capability to produce more power and torque, making it a popular choice among truck enthusiasts.

LLY vs LBZ: A Quick Look

LLY engines don’t feature any EGR or DOC technology and also have less horsepower and torque but their compression ratio is higher than LZB engines, which helps increase engine performance.

On the other hand, the LBZ is powered with 50 additional horsepower. Along with the same turbocharger as LLY, the VVT technology increases its efficiency.

LLY is a detuned version of the LBZ but you can easily make your changes with the tuning mechanism of these engines.

Specifications LLY  LBZ 
Emissions Controls None Exhaust Gas Recirculation (EGR), Diesel Oxidation Catalyst (DOC)
Horsepower 310 hp @ 3,000 rpm 360 hp @ 3,200 rpm
Compression ratio 17.5:1 16.8:1
Turbocharger Garrett GT3788VA Garrett GT3788VA VVT
Torque 520 lb-ft @ 1600 rpm (early ’06: 605 lb-ft @ 1600 rpm) 650 lb-ft at 1,600 rpm
Badges Red Blue
VIN 8 & 10 digit 2 & 6 D & 6
Intake style Passenger side Right angle
Cooler fan 2004.5-19 inch and 2006-21 inch 21 inch
Overheating Yes No
Production 2004 – early 2006 2006 – 2007
  • Emission restriction technology

LLY engines don’t have any Exhaust Gas Recirculation (EGR) or Diesel Oxidation Catalyst (DOC) technology.

On the other hand, the LBZ engine is equipped with both EGR and DOC technologies, which helps reduce emissions of harmful pollutants such as NOx and CO.

If you are concerned about the environment, then the LBZ engine would be an eco-friendly option for you.

  • Horsepower

The LLY engine has a maximum output of 310 hp and operates at a maximum of 3000 rpm, while the LBZ engine has 360 hp and 3200 rpm.

The higher output of the LBZ engine makes it a better option for heavy-duty tasks. However, that won’t matter much for regular and light-duty use.

  • Compression ratio

Generally, a higher compression ratio e.g. 17.5:1(LLY) results in better engine performance and efficiency than 16.8:1(LBZ). But in this case, LBZ engines get ahead with a lower compression ratio.

This is because the best compression ratio of an engine depends on the balance between performance, efficiency, fuel availability, and quality.

  • Turbocharger

LLY engines contain a GT3788VA turbocharger, it’s a high-performance turbocharger known for its quick response and high-end power capabilities.

On the other hand, LZB engines carry out the Variable Valve Timing (VVT) technology with a GT3788VA turbocharger which is used to optimize valve timing and increase engine efficiency, power, and torque.

  •  Torque

The LBZ is known for its high torque output, with a maximum of 650 lb-ft at 1600 rpm. On the other hand, the LLY can produce a maximum of 520/605 lb-ft at 1600 rpm, which is lower than the LBZ.

This makes the LBZ engine a great choice for heavy-duty tasks such as towing, hauling, and off-roading though LLY engine torque output is still sufficient for both light-duty and heavy-duty tasks.

  • Badge color and VIN

The red badges (Duramax diesel) in the VIN indicate LLY engine and blue badges (Allison Duramax) are for LBZ. Moreover, if the eighth and ten digits in the VIN are ‘2’ and ‘6’ they indicate LLY while ‘D’ ‘6’ is for LBZ.

  • Intake style

LBZ’s engine intake style and leverage system is more on the right angle whereas LLY’s is a little on the passenger side.

  • Cooling fan & overheating

The LBZ’s cooling fan is 21 inches with no overheating history. On the other hand, the 19-inch cooling fan of LLY 2004 -2005 models had some overheating issues though they were replaced with a 21-inch cooler later in 2006 to tackle this problem.

  •  Production years

An early version of the LLY was released to the market from 2004 to 2005 and the upgraded version came in early 2006. The LBZ was released from 2006 to 2007 with advanced technologies.

LLY vs LBZ: Are There Any Similarities?

Specifications LLY LBZ
Displacement 403 ci 403 ci
Valve Configuration Overhead Overhead
Valves Per Cylinder 4 4
Assembly Site Moraine, Ohio, USA Moraine, Ohio, USA
Valve Lifters Mechanical roller Mechanical roller
Firing Order  1 – 2 – 7 – 8 – 4 – 5 – 6 – 3  1 – 2 – 7 – 8 – 4 – 5 – 6 – 3
Bore x Stroke 4.055 in. or 103 mm x 3.897 in. or 99 mm 4.055 in. or 103 mm x 3.897 in. or 99 mm
Fuel System Direct injection with high-pressure common rail w/ Bosch CP3 pump Direct injection with high-pressure common rail w/ Bosch CP3 pump
Fuel Type Diesel Diesel
Fuel Tank Size 26 Gallons 26 Gallons
Maximum Powered Speed 3250 rpm 3250 rpm
Block Cast iron w/ deep skirt Cast iron w/ deep skirt
Cylinder Head Cast aluminum Cast aluminum
Intake Manifold Cast aluminum Cast aluminum
Exhaust Manifold Cast nodular iron with a steel pipe extension Cast nodular iron with a steel pipe extension
Main Bearing Caps Cast nodular iron Cast nodular iron
Crankshaft Forged steel Forged steel
Camshaft Steel Steel
Connecting Rods Forged Steel Forged Steel
Engine Oil Capacity 10 qt./9.5L w/ Filter 10 qt./9.5L w/ Filter
Engine Mass Approximately 835 pounds Approximately 835 pounds
Design 90-degree V8 90-degree V8
Bore 4.06 inches 4.06 inches
Stroke 3.90 inches 3.90 inches
Rod Forged-steel, fractured (cracked) cap Forged-steel, fractured (cracked) cap
Pistons Cast-aluminum Cast-aluminum
Heads Cast aluminum with six 14mm diameter head bolts per cylinder (with sharing) Cast aluminum with six 14mm diameter head bolts per cylinder (with sharing)
Valves OHV, four valves per cylinder, single cam OHV, four valves per cylinder, single cam
Injection System Bosch high-pressure common-rail, direct injection Bosch high-pressure common-rail, direct injection
Injectors Bosch solenoid (outside valve cover) Bosch solenoid (outside valve cover)
Injection Pump Bosch CP3 Bosch CP3
Intercooler Air-to-air Air-to-air


About the author

Lillian Kazmierczak

As far as I can remember, I would say I have been a car nut for my whole life. My father was a car dealer who used to change and repair his cars himself. This gave me the opportunity to get around all sorts of cars and get my hands dirty repairing vehicles from an early age.

A great fan of Japanese quality and German preciosity, my deep passion lies in older models that I believe have a flair that takes me back to my childhood! I also love their extraordinary durability and reliability when compared to today’s modern models.

When not out taking a ride, I enjoy socializing with fellow motorheads online and consuming any car facts and figures I can get my mind on!

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